1. Field of the Invention
The present invention relates to an outboard motor equipped with a water-cooled engine that includes an exhaust manifold cooling water jacket for cooling an exhaust manifold for discharging exhaust gas from a combustion chamber to the outside, the exhaust manifold cooling water jacket being supplied with cooling water from a cooling water pump.
2. Description of the Related Art
As an engine for an outboard motor, a water-cooled engine is generally used. It is known from Japanese Patent Application Laid-open Nos. 9-41960 and 10-212948 that cooling is conducted by means of an exhaust manifold cooling water jacket formed so as to cover an exhaust manifold, which is one of high temperature members surrounding the engine.
However, since either of the above-mentioned conventional arrangements includes a pressure relief valve on the downstream side of the exhaust manifold cooling water jacket, if the pressure relief valve closes when the engine runs continuously at low speed, air residing within the exhaust manifold cooling water jacket cannot be smoothly discharged to the outside, and there is a possibility that a local heat trap might be generated.